1. Field of the Invention
The present invention relates generally to apparatus for dispensing a liquid, and more particularly but not by way of limitation, to apparatus for dispensing a herbicide.
2. Discussion
In recent years, farmers have used herbicides to make the task of controlling unwanted plant growth more efficient and the use of such chemicals, along with the use of fertilizers, has played an important part in increasing the output of American agriculture. With the growth of the world's population, it can be expected that these chemicals will continue to be used as a means of attaining crop yields that must be achieved if famine is to be avoided.
However, these chemicals can cause damage if care is not exercised over their release into the environment. Because of this need to control the release of herbicides, such chemicals are no longer provided in small containers which can be discarded after the herbicide has been transferred to a system utilized to apply the herbicide to plants in the field. Rather, herbicide is now supplied in tanks that contain a large quantity of the herbicide for use over a long period of time, and these tanks can be refilled as the needs of a farmer require.
The use of large, refillable tanks in the supply of herbicide to the farmer, while necessary for the protection of the environment, has caused a problem stemming from the length of time that the tanks will contain the herbicide while the supply is drawn down by use. Herbicides are supplied in the form of a high concentration of particulate matter suspended in a liquid and the suspension is diluted with water prior to application to the fields. Thus, the farmer can dilute the herbicide to a concentration that is appropriate to the job at hand by metering the herbicide into a mixing tank that is part of the equipment for applying the herbicide. The problem that has arisen is that the particulate component of the herbicide tends to settle so that the concentration of the particulate component varies throughout the tank in which the herbicide is stored. This variation can result in a substantial increase in agricultural expense. If the herbicide drawn from the tank has too high a concentration of the active particulate matter, it will be applied in an amount that is in excess of that needed. Since herbicides are expensive, overuse of the herbicide can have a serious effect on farm economy. If the herbicide drawn from the tank has too low a concentration, it may be necessary to repeat the application of the herbicide to the field, thereby wasting labor as well as herbicide.